linux-kernel - Re: [PATCH] fix console change race exposed by CFS

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Message-ID: <20070930072056.GA18108@elte.hu>
Date:	Sun, 30 Sep 2007 09:20:56 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jan Luebbe <jluebbe@...net.de>
Cc:	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org
Subject: Re: [PATCH] fix console change race exposed by CFS


* Jan Luebbe <jluebbe@...net.de> wrote:

> From: Jan Lübbe <jluebbe@...net.de>
> 
> The new behaviour of CFS exposes a race which occurs if a switch is
> requested when vt_mode.mode is VT_PROCESS.
> 
> The process with vc->vt_pid is signaled before vc->vt_newvt is set. This
> causes the switch to fail when triggered by the monitoing process
> because the target is still -1.
> 
> Signed-off-by: Jan Lübbe <jluebbe@...net.de>

nifty! I'm wondering what the symptoms of this bug were - how did you 
notice it? Also, i'm wondering how you managed to debug this - looks 
quite hard to trigger this race, right?

Acked-by: Ingo Molnar <mingo@...e.hu>

	Ingo
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